Characterization of acid-resistant aldo–keto reductases capable of asymmetric synthesis of (R)-CHBE from Lactobacillus plantarum DSM20174

Ethyl (R)-4-chloro-3-hydroxybutyrate ((R)-CHBE), as a chiral intermediate, is widely used in the synthesis of various chiral drugs. In this study, we screened two aldo–keto reductases (LP-AKRs) from the probiotic Lactobacillus plantarum DSM20174, both with a molecular weight of approximately 31 kDa. Both enzymes could reduce 4-chloroacetoacetic acid ethyl ester (COBE) to produce (R)-CHBE with an enantioselectivity value of 99%. When determining the kinetic parameter, the Km, Kcat, and Vmax of LP-AKR5 and LP-AKR9 were 9.5 mM, 7.6 U/mg, 3.96 s−1 and 8.7 mM, 8.59 U/mg, 4.47 s−1, respectively. Both LP-AKR5 and LP-AKR9 had an optimal reaction pH of 6 and could maintain a high level of stability at pH 6, allowing them to perform well in an acidic environment. LP-AKR5 and LP-AKR9 had optimal reaction temperatures of 30 °C and 40 °C, respectively. Metal ions had minimal influence on LP-AKR5 and LP-AKR9 enzyme activities. This series of enzymatic properties showed that LP-AKR5 and LP-AKR9 mined from Lactobacillus plantarum DSM20174 could asymmetrically catalyze the synthesis of (R)-CHBE under weakly acidic circumstances, which could maintain product stability and provide a good foundation for industrial production.